This invention relates to the field of optical communication systems and, in particular, to the field of bidirectional optical communication links within such systems wherein a single optical communication link transmits a plurality of carrier wavelengths.
Optical networks having a plurality of optical transmission lines permit high bandwidth data communications. In optical data networks high speed data is modulated on light waves that are transmitted through the optical links of the data network. Optical transmission links or lines of this type can be used in telephone systems and various other types of data communication systems. Further bandwidth improvement can be achieved in an optical network by modulating different electrical data signals on distinct light wave carriers wherein each light wave carrier has a different wavelength. This technique is known as wavelength division multiplexing (WDM). Optical systems using WDM therefore require a plurality of optical transmitters and optical receivers operating at different light frequencies.
When several light wave carriers operate within the same optical fiber, as in the case of WDM, unwanted interference signals can sometimes be formed in the available optical band of the fiber. For example, second harmonic distortion can produce sums of differences of the traveling wavelengths that can tend to lie outside the band of interest. However, third harmonic distortion can be within the band of interest and therefore have an interfering effect on the carrier spectrum. Interference of modulated signals with each other in this manner is referred to as crosstalk.
Several techniques are known in the prior art for minimizing the crosstalk between modulated signals within optical fibers. For example, it is known to select the transmission frequencies of modulated signals within an optical fiber such that the possible interference frequencies of the modulated signals do not fall within the transmission bands of other modulated signals within the fiber. Additionally, it is known to restrict the modulation bandwidths of an optical fiber in order to minimize crosstalk. Furthermore, it is known to provide guard bands between adjacent wavelengths of an optical fiber. However, each of these techniques is hindered by the limited selectivity and stability of the optical filters required for implementation.
Therefore, it is desirable to provide an improved system and method for optimizing system performance within optical fibers transmitting modulated wavelengths that overcomes the drawbacks of the prior art methods.
The present invention is a system and method for communicating information within a bidirectional optical link having a plurality of wavelengths that transmits information in a first direction receiving information and from a second differing direction. First and second sets of wavelengths of the plurality of sequential wavelengths are determined wherein the wavelengths of the first set alternate with the wavelengths of the second set. The first set of wavelengths is transmitted in a first direction and the second set of wavelengths is transmitted in a second direction such that the propagation directions of adjacent wavelengths differ from each other.